She's lucky she didn't die. There's a rare condition that could be described as an "allergy to cocaine"--anticholinesterase deficiency--in which the body doesn't process cocaine and excrete it, it circulates continuously until the patient O.D.'s. This can happen with a very small amount of cocaine, like 10-20mg or so. It's also possible that she's allergic to something that was used to cut it. Hope OP's sister is OK. (I am not a medical